1. Field of the Invention
The invention relates to a dressing such as a wound care dressing being capable of providing enzymatic debridement.
2. Description of the Related Art
In the treatment of chronic wounds it is often a problem that the wound comprises necrotic or non-viable tissue and slough. The presence of these substances renders it difficult for the wound to heal properly as well as it may inhibit the function of the wound dressing by preventing that any active ingredient of the dressing may reach the wound bed. Furthermore, the slough may block/clot the surface of the dressing thus preventing the upper layers of the dressing to function. Finally, the presence of necrotic tissue and slough may give rise to undesired bacterial growth. Therefore it is well known to debride such wounds e.g. by sharp, mechanical or autolytic debridement. It is also possible to use proteolytic enzymes to debride a wound and several ointments and sprays has been marketed for this purpose. Those ointments and sprays typically work within a limited period of time, and thus these products have to be applied repeatedly, e.g. two or three times a day. A consequence of this would be to remove the dressing several times a day for application of ointment, which would be highly undesirable due to the trauma to the skin and the patient as such, during change of dressings. Furthermore, none of these products have the capacity to handle the liquefied slough and degraded necrotic tissue generated by the enzymes.
U.S. Pat. No. 4,668,228 discloses a debriding tape comprising an adhesive mass on a non-gel, non-bioerodable, biocompatible occlusive or semi-occlusive backing, where an effective amount of a debriding enzyme in dry powdered form is situated on the adhesive surface. When the powder is brought into contact with wound exudates the entire load of enzymes is released immediately. This dumping of enzymes may be suitable for burns but it may not be considered optimal when dealing with chronic wounds, where a sustained release of enzyme over a prolonged period often is desired.
CA Patent No. 2,011,220 discloses a material with biological activity comprising a carrier in the form of a textile, an enzyme immobilized on, and covalently bound to the carrier, 0.02-0.50% wt enzyme, 99.50-99.98% wt carrier. When the enzymes are covalently bound to the carrier they may either stay bound during use, or the may be released when a specific enzyme, which is capable of cutting the bond, is present in the wound. If the enzymes stay bound to the carrier, the dressing will only have an effect on the surface of the wound. The enzymes will not reach the deeper layers and the debridement of the wound will be non-sufficient. If an enzyme capable of cutting this bond is present in the wound, the proteolytic enzyme will be released, but the patient-to-patient variation of the amount of enzyme present is typically significant, meaning that the degree of the debridement may vary. Furthermore, in patients suffering from dry necrosis, the enzymes in the wound may not be able to penetrate the necrosis and no therapeutic enzyme will therefore be released. In general, this method will release the greatest amount of debriding enzymes in areas where there is less necrosis and therefore less need of debridement.
In U.S. Pat. No. 5,206,026 is disclosed a film for instantaneously delivery of enzymes to a wound. When exposed to aqueous liquid the film rapidly dissolves, thus releasing its contents of enzymes simultaneously. No long-term release in the form of a controlled release is disclosed; on the contrary, a burst release is desired here.
In US patent application No. 2002/0114798 is disclosed an enzymatic wound debrider that uses a combination of a proteolytic enzyme and an anhydrous hydrophilic poloxamer carrier. The debrider is in the form of an ointment or gel and the reference is silent with respect to any absorbent properties of the debrider as well as the release profile.
Thus there is still a need for a wound dressing being capable of releasing proteolytic enzymes over a prolonged period. This invention has as its primary objective the fulfillment of the above-described need.